Make it easier to know if you're installing the latest version of a package

[ulfaslak]

Problem description

Pixi uses the Anaconda package registry as a default, and that's fine for working with main-stream packages, but once you start using more fringe/cutting-edge packages, then it's nearly always the case that the conda version of the package you need is outdated.

The problem, then, is that Pixi doesn't warn about this. I'll often install a package and then only much later discover that I've been using an outdated version.

This is a problem. I always want the latest stable version of packages I'm installing. There should be a flag enforcing this. Consider the following example:

pixi add --force-latest outlines torch torchvision pillow

This will install outlines, torch and torchvision through PyPI because that registry offers the latest version, while pillow gets installed from Anaconda.